Woo hoo. RBSicon have paid up £1,773.

After initial problems of getting hold of bank statements, the time from preliminary letter for repayment to settlement was just over a month.

Preliminary approach letter - 10 May
RBS acknowledgement - 11 May
letter before actionicon - 29 May
RBS letter offering full amount as "gesture of goodwillicon" - received 2 June
Acceptance of RBS offer - 4 June
Cheque received - 14 June

Many thanks for all the guidelines and help available on here. Have already recommended this site to my friends.